But the BBC's Juliana Liu in Hong Kong says crowds on Connaught Road in the Central district on Thursday morning were at their lowest ebb since the protest began.

Organisers have attributed this to sheer exhaustion, as the demonstration stretches into its fifth day, she says.

Media captionThe US and China expressed different views about events in Hong Kong

'High hopes'

The protesters include students, supporters of pro-democracy group Occupy Central and others angered by the initial police response to rallies at the weekend, which included using tear gas.

Mr Wang, the most senior Chinese official to speak openly on the matter, said: "Hong Kong affairs are China's internal affairs. All countries should respect China's sovereignty. For any country, for any society, no-one will allow those illegal acts that violate public order."

Image copyrightAFPImage caption
Protesters have been sleeping on roads around government buildings for several days

But he said he believed Hong Kong authorities had "the capability to properly handle the current situation in accordance with the law".

Mr Kerry said the US supported universal suffrage in Hong Kong, adding he hoped local authorities would "exercise restraint and respect for the protesters' right to express their views peacefully".

In China, state TV said Hong Kong's police should be supported in their attempts to "restore the social order as soon as possible".

An editorial in the Chinese Communist Party's newspaper People's Daily on Thursday called the situation "chaos".

"Hong Kong has for many years enjoyed peace and harmony. It now sees the emergence of this embarrassing 'chaos', and the root cause lies with a few people who are disrespecting the law.... 'chaos' denies Hong Kong residents their prosperity, goes against their wishes, and is not what all Chinese people wish to see or what we can tolerate."

Juliana Liu, BBC News, Hong Kong

The senior Chinese leadership has set out clear limits on who can run for the position of chief executive, Hong Kong's top leader, in 2017.

The rules make it virtually impossible for anyone not trusted by the Chinese government to stand for election.

As a result, the protesters accuse Beijing of reneging on decades of vows to give Hong Kong people genuine democracy.

But although there is widespread anger that Beijing may have violated the spirit of the agreements it has made, there is intense debate over whether it has violated the letter of the law.